Circuit breaker with conductive and insulating particles



Jan. 14, 1969 v H. GREBER 3,422,455

CIRCUIT BREAKER WITH CONDUCTIVE AND INSULATING PARTICLES Filed June 8, 1965 BLOWER INVENTOR United States Patent 4 Claims ABSTRACT OF THE DISCLOSURE This invention is related to a circuit breaker in which a mixture of 50% to 50% of conductive and nonconductive powder particles is introduced into the arc space between the stationary and movable contacts at the moment of current interruption. For this purpose, the housing containing the stationary and the mobile contacts is turned around by 180 degrees about its horizontal axis, so that the powder mixture is lifted and then falls down, and while so doing, fills the open space between the separated contact pairs. Another way to introduce the powder mixture into the space between the opened contact pairs is to blow it in by means of a blower.

The purpose of this invention is to provide a simple and inexpensive circuit breaker of great current interrupting capacity. To achieve this purpose the following physical phenomenon is applied. If the distance between two conductive particles is decreased, also the voltage necessary to breakdown the distance between them becomes smaller. From a certain very small distance, however, its further decrease does not entail a concomitant decrease of the breakdown voltage. From this results, that in a cloud of conductive particles the potential dilference necessary to breakdown the distance between two nearby ones is constant. If the number of particles per unit of volume of the cloud is great enough, and if such cloud is introduced between the mobile and stationary contacts of a circuit breaker, the potential difference between these contacts may not be suificient to create an are between these particles, because the spacing between these particles is not sufficient to sustain an are.

This invention pertains essentially to an air circuit breaker, in which conductive particles are introduced into the space between the mobile contact departing from the stationary. Since by application of this method air circuit breakers are feasible of an interrupting capacity equal and surpassing that of oil, and sulfur-hexafiuoride circuit breakers, a purpose of this invention is to do away with oil and sulfur-hexafluoride as fillers for breakers.

If insulating particles are added to the conductive ones introduced into the gap between the departing contacts, the effectiveness of this circuit breaker can be increased, by enhancing the dielectric strength of the gap.

Methods to apply the above described principles will be shown in the following specification and in the accompanying drawing. In this drawing, FIGURE 1 represents a longitudinal cross section of a one pole breaker, in which opening of its contacts is accomplished by turning its enclosure 180 degrees around its horizontal axis.

In FIGURE 2 can be seen the same breaker in its turned position, with its contacts open. As shown in FIGURE 3, the conductive particles themselves can constitute the "ice mobile contact. Such breaker, in the moment when it opens the circuit, is shown in FIGURE 4. The same breaker is shown a third time in FIGURE 5, in which the application of a bypass switch is indicated. In FIGURE 6 can be seen a logitudinal cross section of an air circuit breaker in its simplest form of a knife switch, around which its enclosure can rotate around its horizontal axis. The same switch with its enclosure turned degrees can be seen in the cross section shown in FIGURE 7. FIGURE 8 and FIGURE 9 show a transverse and a longitudinal cross section, respectively, of a simple knife switch provided with a scoop for lifting the conductive powder; and FIGURES l0, and 11 represent the same cross sections with the scoop releasing the conductive powder into the space between the contacts.

In consideration of the details shown in FIGURE 1, it can be seen that a simple knife switch consisting of blade 1, which can be turned in contact 2, fits into jaw 3. Contact 2 is connected to conductor 4, by means of bolts 5. Similarly, jaw 3 is connected to conductor 6, by means of bolts 7. On one end of blade 1 is fixed a heavy weight 8. The knife switch whose parts have just been mentioned is mounted within enclosure 9, made of insulating material. This enclosure can be of circular, square or in any other way shaped cross section. Enclosure 9 is turnable in the bearings 10, and 11, into which fit the short shafts 12 and 13. These shafts are fastened to enclosure 9 through the intermediary of flanges 14, and 15. By means of the levers 16, 17 and 18, solenoid 19 can turn enclosure 9, 180 degrees around its longitudinal axis. The bearings, the linkage mechanism and solenoid 19 are all shown diagramatically. Solenoid 19 is actuated with a relay, which is not shown in the drawing, since it is not a part of this invention. The grit, which is the most important part of this invention is designated with the numeral 20. Essentially, this grit is conductive and consists either of metallic particles, or granules of a semiconductor such as graphite. However, as mentioned, the effectiveness of this breaker can be increased by addition of insulating powder, such as ground glass or porcelain. The proportion in which the two kinds of granulated materials are mixed is about 50% to 50%. Moreover, the two kinds of granules can be combined by coating the conductive particles with a thin layer of insulating material. This can be easily accomplished by coating metallic or semiconductive granules with enamel, shellac or plastics. Even simpler than this is anodizing of aluminum particles, or oxidizing particles of silver or copper.

In FIGURE 2, is shown exactly the same breaker, turned upside down, by its rotation around its horizontal axis. The numerical designation of the parts of the breaker is the same as used in FIGURE 1. Wires 4 and 6 have sufiicient slack in order not to interfere with the rotation of the breaker. In the rotated position, weight 8 pulls out blade 1 from jaw 3. The granulated material 20, brought by rotation of the breaker to the top falls down by gravity. The falling down grit 20 fills the space between jaw 3 and then pulled out from blade 1. Filling this space with grit 20, of the described composition, is essential to the operation of this breaker.

The principle of operation mentioned at the beginning of this specification can be embodied in many other ways. FIGURES 3 and 4 give another example of application of this inventive idea. In this embodiment enclosure 21,

is, just as enclosure 9 in FIGURES 1 and 2, rotatably mounted in the bearings 22 and 23. The short shafts 24 and 25, are fastened to enclosure 21, by means of flanges 26 and 27. Enclosure 21 is made of insulating material. For simplicity sake, and in order not to obscure the essence of this invention, the solenoid and relay with the current transformers serving to rotate this enclosure 180 degrees around its horizontal axis, are not shown. Enclosure 21 contains two metallic contacts 28 and 29, which by means of bolts 30 and 31 are connected to wires 32 and 33 respectively. In this embodiment it is preferable, but by no means mandatory, that grit 34 consists only of conductive particles. Since it is conductive, grit 34 bridges the contacts 28 and 29 and closes the circuit in which the breaker is inseited. In FIGURE 3 the same breaker is shown in its upside down position, when it is turned 180 degrees around its horizontal axis. Contacts 28 and 29 assume now their position on top of the enclosure. Grit 34, which was laying in compact consistency on bottom of enclosure 21, is now carried to the top of the enclosure by its rotation. Due to gravity, grit 34 falls down from the top of the enclosure toward its bottom. By doing so, this grit 34, forms, a cloud of conductive particles filling the space between the contacts 28 and 29. This cloud of conductive particle is essential for operation of this breaker.

In some application the resistance, and the predicated on it voltage drop between the contacts 28 and 29, may be objectionable. To overcome such objection, a bypass switch can be used as shown in FIGURE 5. The same breaker as shown in FIGURES 3 and 4, is drawn again in FIGURE 5, in which the same numerical designation of its parts is used. It can be seen in this figure that contacts 28 and 29 are bypassed with a knife switch 35, shown diagrammatically. Bolts 30 and 31 are omitted in FIGURE 5. In order to let the conductive grit 34 do the interruption of the current, and not to leave it to the bypass switch 35, this switch has to be opened before the main breaker opens. For the same reason it has to close after the main breaker has closed. The bypass switch is an electromagnetically operated switch, and also the main breaker is operated by means of a solenoid. The coordination of the two current interrupting devices by means of relays presents no problems. Since it is not a part of this invention, no attempt is made to show these relays and their interconnection in this drawing.

In the preceding examples it is shown that the enclosure together with its enclosed breaker are rotated around their horizontal axis. While the rotation of the enclosure is indispensable, rotation of the enclosed breaker contacts is not. This point is brought out in FIGURES 6 and 7. FIGURE 6 shows an enclosure, on the bottom of which grit 37 is deposited. Grit 37 can be a half and half mixture of conductive and insulating particles. Conductors 38 and 39 are copper or aluminum rods which lead the current through jaw 40, blade 41, and contact 42. These rods serve also as pivots around which enclosure 36 can rotate. During this rotation contact 42, and jaw 40, both mounted on insulating plate 43, remain stationary, but blade 41 is pulled out from jaw 40, by means of a solenoid also comprised in enclosure 36, but not shown for simplification of the description. The grit is designated with the numeral 44.

FIGURES 8, 9, and 11 demonstrate still another embodiment of this inventive idea. In FIGURE 8 is shown the transversers, and in FIGURE 9 the longitudinal cross section of a breaker whose contact 45, blade 46 and jaw 4-7 and also grit 49 are enclosed in the insulating housing 48, of square cross section. Neither the elements of the switch, nor the enclosure is rotated. Grit 49 is lifted by means of a scoop 50, which is attached to blade 46. This scoop 50 is simply a box having reeds 51 and 52 attached to its bottom, as can be seen in FIGURE 8. In closed position of the breaker, scoop 50 is immersed into the granulated material 49 so that reeds 51 and 52 are bent upward and let the grit into the scoop 50. Reeds 51 and 52 are so hinged that they can remain horizontal, or they can be bent upward. The longitudinal section of the switch is shown in FIGURE 9, in which the same numerical designation of the parts of the switch is maintained. When the breaker is opened, blade 46 is moved upward by a solenoid, which is not shown. While moving upward, blade 46 takes with it scoop 50 with the contained in it sandy material. When the scoop is lifted, reeds 51 and 52 take on a horizontal position. In this position the sandy grit is poured out through the gaps 53 and 54, between the reeds 51 and 52 and the blade 46. This is shown in the transverse section in FIGURE 10, in which the breaker is drawn in its open position. The grit poured out from the gaps 53 and 54 fills the space between the jaw and the blade 46, which is essential for operation of this breaker. The longitudinal cross section of this breaker in open position is shown in FIGURE 11.

If metallic particles are introduced into the arc space between the separate stationary and mobile contacts of a circuit breaker at the moment of current interruption, the total gradient of the potential between the corresponding contacts is broken down into partial ones between the discrete conductive particles. To break down a very small distance between two neighboring particles a certain minimal voltage is required. Additional functions of the conductive particles are: they absorb some heat, and

thereby cool the arc, they also form a convenient platform for the positive, relatively heavy, ions to settle down, and thereby become immobile. If the particles introduced into the arc space at current interruption are nonconductive, they also contribute to the interruption of the arc. They absorb some heat, and capture some positive ions. They stand in the way of the arc and force it to go around them, so that its length is increased. By mixing the conductive with the insulating particles, however, effects can be produced which could not be achieved by either of the two kinds taken separately. In such mixture, direct contacts between two or more conductive particles are prevented. The ar-clet between two neighboring conductive particles is elongated, because it has to go around nonconductive particles which is likely to be in its way. Nevertheless, a mixture of conductive and nonconductive particles forms a conductive path, if they are stacked in one layer, as shown in FIGURES 3 and 5, for example.

Numerous as they are, the above described modes of application or" this inventive concept do not exhaust all of its possible applications. Many more ditferent applications, modifications and variations of this invention are possible, all in its spirit as defined by this specification and by the following claims:

Iclaim:

1. A circuit breaker comprising an insulating enclosure, separable stationary and movable contact means mounted in said enclosure, means for introducing an about 50% to 50% combination of conductive and insulating particles into the space between the stationary and movable contact means at their separation, such particles initially lowering the potential gradient between them, cooling the arc, capturing the positive ions in the arc space, elongating the arc, and thereby contributing to the interruption of the arc.

2. A circuit breaker as in claim 1, with said particles consisting of conductive particles covered with a thin layer of insulating material.

3. A circuit breaker as in claim 1, consisting essentially of a knife switch mounted inside said insulating enclosure, having said mixture of conductive and insulating particles at its bottom, with said mixture falling down into the gap between the stationary and mobile contacts at their separation, when said enclosure is turned upside down after its rotation degrees around its horizontal axis.

4. A circuit breaker as in claim 1, with said mixture of conductive and insulating particles blown into the space between said stationary and mobile contact means at their separation, with these particles being carried into this space by means of a stream of an insulating fluid.

References Cited UNITED STATES PATENTS Thomson 200 149 5 Pittman et al. 200120 Mueller ZOO-61.52

Lohausen 200-135 Minc'h 6 FOREIGN PATENTS 506,449 9/ 1930 Germany. 1,166,324 3/ 1964 Germany.

383,265 7/ 1933 Great Britain.

ROBERT S. MACON, Primary Examiner.

U.S. C1. X.R. 

